Low frequency oscillations in blood pressure (BP) can occur due to a feedback pathway between the sensing of BP and the central nervous system (CNS), often termed the baroreflex, affecting both cardiac output (heart-rate and stroke volume) and peripheral resistance. In this paper, an integrated model of both these subsystems is assembled and an analysis technique developed, which shows the conditions under which a limit cycle oscillation can occur. In particular, the role of mean levels of cardiac output and peripheral resistance, previously thought to be relatively unimportant, in establishing and maintaining sustained oscillations, is highlighted. The ultimate aim of this analysis is to assist in the development of diagnostic tests based on measurement of low-frequency blood pressure oscillations.